NEW YORK—Just as a true outbreak might, the new viral thriller Contagion, opening this weekend, begins unremarkably enough. A simple cough, heard against a black screen.

This is no ordinary hack, of course. Aside from coming from the lovely, if peaked, Beth Emhoff (Gwyneth Paltrow) passing time at a Chicago O'Hare airport bar, this cough kicks off a rapid-paced epidemiological thriller that has silver screen scientists (Marion Cotillard, Jennifer Ehle, Laurence Fishburne, Kate Winslet and others) in a race to save the globe from a novel fatal virus.

As a bottom title on the first scene notes, however, the cough occurs on "Day 2," setting it up as neither the beginning nor the end of the spread. The mysteries, as in a real epidemiological case, unfold both backward and forward in time, sending the scientists and viewers in search of answers to two key questions: What happened on "Day 1" to start the spread; and how many days—and deaths—are going to tick by before the virus is contained?

We soon learn that Emhoff is en route home to her husband (Matt Damon) in Minneapolis from a business trip to Hong Kong. Over the next couple days, people in Tokyo, Hong Kong, Chicago, London and elsewhere start to drop like flies—coughing, running fevers, having seizures, and frequently dying. It isn't long until Emhoff, herself, is having her brain examined by two doctors, who get a shock when they look inside:

"Should I call someone?" the attendant asks. "Call everyone," the other replies.

And soon enough, U.S. Centers for Disease Control and Prevention (CDC) infectious disease expert Ellis Cheever (Fishburne) is shipping epidemiologist Erin Mears (Winslet) off to Minneapolis, where she gives the local health department—and the audience—a quick lesson on R-0 ("R-naught" or basic reproductive number, the rate at which one person is likely to infect others with any given disease; the 1918 Spanish flu was roughly two to three, smallpox was closer to five to seven).

As the apparent R-0 for the new virus continues to climb as it spreads around the globe, World Health Organization official Leonora Orantes (Cotillard) tracks down the point of first human spread to a Hong Kong casino that Emhoff visited. And researchers in the U.S. at the CDC, including Ally Hextall (Ehle), are hard at work trying to develop a vaccine. Rumors about a homeopathic treatment, spread by renegade blogger Alan Krumwiede (Jude Law), spur looting at pharmacies that precipitate a breakdown of law and order. As the death toll climbs into the millions, a scruffy and apparently immune Mitch Emhoff (Damon) soldiers through, attempting to protect his teenage daughter from infection.

To avoid a slipping too far into science fiction melodrama, those behind the film roped in real-world scientific expertise early on. Ian Lipkin, director of the Center for Infection and Immunology Columbia University's Mailman School of Public Health, started working with the film's writers in 2008. He remembers asking them when the movie was first pitched, "Is this going to be like Outbreak or I am Legend—or do you want to make a serious movie," he recalled at an advance screening in New York City last month.

It turns out they wanted to make a serious movie. And they mostly succeeded. "We had Kate Winslet learning how to pipet," he says, noting that he consulted with the writers and was invited to review sets and costumes and sit in on most of the filming to keep the science straight. In one scene Hextall (Ehle) injects herself with an experimental vaccine. An original take had her jabbing herself through her stockings, but, Lipkin pointed out, no respectable researcher would be so sloppy. So, instead, they returned to the scene to re-shoot later, having her first remove her tights.

In addition to making sure the actors were acting like proper scientists in the biosecurity level four shots, the movie's makers also wanted to make the virus itself believable. Craig Street, a senior bioinformatics analyst who works with Lipkin at Columbia, helped to design the film's fictional virus, MEV-1. (Viral spoiler alert: To do this they created a detailed model of a recombined bat nipah virus and a porcine rubulavirus, which are both in the paramyxovirus family—which also includes hendra virus as well as infections that can cause childhood pneumonia).

Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases at the National Institutes of Health, also attended the August screening and said he found the movie to be "among the best—if not the best" disease-centered movie, from a scientific perspective. Although the speed that a vaccine was developed, manufactured and distributed (144 days) "seemed unrealistic," he said (it took closer to six months to get the first doses of the H1N1 vaccine out in 2009), the rest was "very scientifically accurate."

What caught Fauci's eye was the way the disease spread to—and among—humans: by simple interaction. Early on in the film, when the source and type of the virus are still a mystery, officers at the Department of Homeland Security are concerned that the virus was a bioterror weapon planted by terrorists to coincide with the American holiday of Thanksgiving for optimal spread. Cheever knows better. "Someone doesn't have to weaponize the bird flu—the birds are already doing that." And that is exactly right, says Fauci, despite all of the and worry about and money to prevent human bioterrorism, it is still the case that "Nature's the greatest bioterrorist."

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